#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int fit(int m)
{
	int i=1, x = 1, y = 1, z=1;
	while (i<=m-2)
	{
		z = x + y;//1 1 2 3 5
		x = y;
		y = z;
		i++;
	}
	return z;
}
int main()
{
	int m = 1;
	scanf("%d", &m);
	int n = fit(m);
	printf("%d", n);
	return 0;
}